The present invention relates to an eyeglass lens processing apparatus for processing a peripheral edge of an eyeglass lens.
A high curve frame having large curvature has been mainly used for sunglasses, but a demand for using a corrective lens together with the high curve frame has been increased. Since it is necessary to use an eyeglass lens having large curvature in case of fitting a lens into the high curve frame, it is desirable to form a high curve bevel in the peripheral edge of the lens so as to correspond to the curvature of the frame. As a method of forming a high curve bevel while restricting bevel thinning (a phenomenon in which a width or a height of the bevel becomes small), a method of separately processing a front slope and a rear slope of a bevel is disclosed (Japanese Patent Application Laid-Open No. H11-48113 (U.S. Pat. No. 6,089,957)), and a method of forming a bevel using a beveling grindstone having a diameter smaller than that of a large-diameter beveling grindstone used for a general beveling is disclosed (Japanese Patent Application Laid-Open No. 2004-74346 and Japanese Patent Application Laid-Open No. 2005-74560 (EP 1510290A1)).
Incidentally, in some cases, the high curve frame mainly used for the sunglasses is provided with a portion in which a side wall Fb formed on a rear surface side of the lens is larger than a side wall Fa formed on a front surface side of the lens as shown in FIG. 7 (hereinafter, the large portion formed on the rear surface side of the lens is referred to as a protrusion portion BH) in order to prevent the lens from being slipped out in a direction toward the rear surface side of the lens. Since the sunglass lens is thin, it is possible to directly fit the lens into the frame by forming the bevel in the peripheral edge of the lens. However, in case of forming the bevel in the corrective lens, since the lens is thick, it is not possible to fit the lens into the high curve frame having the protrusion portion BH just by forming the bevel in the general method. In this case, in order to cope with this situation, the rear surface side of the bevel may be manually cut out by a tool such as a reamer. However, it takes particular skill and much processing time to carry out the processing.